Contemporary Statewide Practice Pattern Assessment of the Palliative Treatment of Bone Metastasis.
CONCLUSIONS: Bone metastases represent a heterogeneous disease, and radiation therapy for bone metastases is similarly diverse. Future work is needed to understand the barriers to single fraction use, and clinical trials are necessary to establish appropriate guidelines for the breadth of this complex disease. PMID: 29726364 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 7, 2018 Category: Physics Authors: Spratt DE, Mancini BR, Hayman JA, Boike T, Pierce LJ, Moran JM, Dominello MM, Fireman M, Griffith K, Jolly S, Michigan Radiation Oncology Quality Consortium Tags: Int J Radiat Oncol Biol Phys Source Type: research

Adaptation of stochastic microdosimetric kinetic model for charged-particle therapy treatment planning.
In this study, we modified the SMK model to shorten the computation time and to reduce the memory space required for the computation. By using the dose-averaged cell-nucleus specific energy per event [Formula: see text] in the SMK formalism, the stochastic nature of z n was reflected onto the estimated cell-survival fractions. The accuracy of the modified SMK model was examined through the comparison between the estimated and the measured survival fractions of human salivary gland tumor cells and V79 cells. We then implemented the modified SMK model into the in-house treatment planning software for scanned charged-particle...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Inaniwa T, Kanematsu N Tags: Phys Med Biol Source Type: research

Improvements in pencil beam scanning proton therapy dose calculation accuracy in brain tumor cases with a commercial Monte Carlo algorithm.
Conclusions: our results suggest that in PBS proton therapy range shifter (RS) need to be used with extreme caution when planning the treatment with an analytical algorithm due to potentially great discrepancies between the planned dose and the dose delivered to the patients, also in case of brain tumours where this issue could be underestimated. Our results also suggest that a MC evaluation of the dose has to be performed every time the RS is used and, mostly, when it is used with large air gaps and beam directions tangential to the patient surface. . PMID: 29726402 [PubMed - as supplied by publisher] (Sourc...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Widesott L, Lorentini S, Fracchiolla F, Farace P, Schwarz M Tags: Phys Med Biol Source Type: research

Feasibility study of Fe < sub > 3 < /sub > O < sub > 4 < /sub > /TaO < sub > x < /sub > nanoparticles as a radiosensitizer for proton therapy.
Feasibility study of Fe3O4/TaOx nanoparticles as a radiosensitizer for proton therapy. Phys Med Biol. 2018 May 04;: Authors: Ahn SH, Lee N, Choi C, Shin SW, Han Y, Park HC Abstract We investigated the feasibility of using multifunctional Fe3O4/TaOx (core/shell) nanoparticles, developed for use in contrast agents for computed tomography (CT) and magnetic resonance imaging (MRI), as dose-enhancing radiosensitizers. First, to verify the detectability of Fe3O4/TaOx nanoparticles in imaging, in vivo tests were conducted. Approximately 600 mg/kg of 19-nm-diameter Fe3O4/TaOx nanoparticles dispersed in phosph...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Ahn SH, Lee N, Choi C, Shin SW, Han Y, Park HC Tags: Phys Med Biol Source Type: research

A novel approach for quantitative harmonization in PET.
raj R Abstract Positron emission tomography (PET) imaging allows for measurement of activity concentrations of a given radiotracer in vivo. The quantitative capabilities of PET imaging are particularly important in the context of monitoring response to treatment, where quantitative changes in tracer uptake could be used as a biomarker of treatment response. Reconstruction algorithms and settings have a significant impact on PET quantification. In this work we introduce a novel harmonization methodology requiring only a simple cylindrical phantom and show that it can match the performance of more complex harmonizat...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Namías M, Bradshaw T, Menezes VO, Machado MAD, Jeraj R Tags: Phys Med Biol Source Type: research

Development of TlBr detectors for PET imaging.
ll GS Abstract Thallium bromide (TlBr) is a promising semiconductor detector material for positron emission tomography (PET) because it can offer very good energy resolution and 3-D segmentation capabilities, and it also provides detection efficiency surpassing that of commonly used scintillators. Energy, timing, and spatial resolution were measured for thin (&lt;1 mm) TlBr detectors. The energy and timing resolution were measured simultaneously for the same planar 0.87 mm-thick TlBr device. An energy resolution of (6.41.3)% at 511 keV was achieved at -400 V bias voltage and at room temperature. A timing resol...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Ariño-Estrada G, Du J, Kim H, Cirignano LJ, Shah KS, Cherry SR, Mitchell GS Tags: Phys Med Biol Source Type: research

Correction factors for ionization chamber measurements with the & quot;Valencia & quot; and & quot;large field Valencia & quot; brachytherapy applicators.
Correction factors for ionization chamber measurements with the &quot;Valencia&quot; and &quot;large field Valencia&quot; brachytherapy applicators. Phys Med Biol. 2018 May 04;: Authors: Gimenez-Alventosa V, Gimenez V, Ballester F, Vijande J, Andreo P Abstract Treatment of small skin lesions using HDR brachytherapy applicators is a widely used technique. The shielded applicators currently available in clinical practice are based on a tungsten-alloy cup that collimates the source-emitted radiation into a small region, hence protecting nearby tissues. The goal of this manuscript is to ev...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Gimenez-Alventosa V, Gimenez V, Ballester F, Vijande J, Andreo P Tags: Phys Med Biol Source Type: research

Activation of QA devices and phantom materials under clinical scanning proton beams - a gamma spectrometry study.
This study focuses on devices manufactured by IBA Dosimetry GmbH: MatriXX PT, PPC05, Stingray, Zebra, Lynx, a Blue Phantom rail and samples of RW3, PMMA, titanium, copper and carbon fibre plastic. Monitor Units (MU) were monitored during delivery. Gamma spectrometry was then performed for each item using a HPGe detector, with a focus on longer lived gamma emitting radionuclides. Activities were quantified for all found isotopes and compared to relevant legal limits for exemption and clearance of radioactive objects. Activation was found to be significant after long irradiation sessions, as done during commissioning of a pr...
Source: Physics in Medicine and Biology - May 4, 2018 Category: Physics Authors: Hanušová T, Johnová K, Navrátil M, Valenta J, Müller L Tags: Phys Med Biol Source Type: research

Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields.
CP Abstract For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, radiation and imaging isocenter test, however, it has to be shown first that PG reveals comparable results as the conventionally applied films. Therefore star shot measurements were performed at a lin...
Source: Physics in Medicine and Biology - May 3, 2018 Category: Physics Authors: Dorsch S, Mann P, Lang C, Häring P, Runz A, Karger CP Tags: Phys Med Biol Source Type: research

Luminescence imaging of water during uniform-field irradiation by spot scanning proton beams.
Abstract Luminescence was found during pencil-beam proton irradiation to water phantom and range could be estimated from the luminescence images. However, it is not yet clear whether the luminescence imaging is applied to the uniform fields made of spot-scanning proton-beam irradiations. For this purpose, imaging was conducted for the uniform fields having spread out Bragg peak (SOBP) made by spot scanning proton beams. We designed six types of the uniform fields with different ranges, SOBP widths and irradiation fields. One of the designed fields was irradiated to water phantom and a cooled charge coupled device ...
Source: Physics in Medicine and Biology - May 3, 2018 Category: Physics Authors: Komori M, Sekihara E, Yabe T, Horita R, Toshito T, Yamamoto S Tags: Phys Med Biol Source Type: research

Reconstruction-of-difference (RoD) imaging for cone-beam CT neuro-angiography.
Conclusions: The RoD approach demonstrated superior performance in 3D angiography compared to FBP and PL in all simulation and physical experiments, suggesting the possibility of CBCT-A on low-cost, mobile imaging platforms suitable to the point-of-care. The algorithm demonstrated accurate reconstruction with a high degree of robustness against data sparsity and inconsistency. . PMID: 29722296 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - May 3, 2018 Category: Physics Authors: Wu P, Stayman JW, Mow M, Zbijewski W, Sisniega A, Aygun N, Stevens R, Foos DH, Wang X, Siewerdsen JH Tags: Phys Med Biol Source Type: research

4D cone-beam computed tomography (CBCT) using a moving blocker for simultaneous radiation dose reduction and scatter correction.
Abstract Four-dimensional (4D) X-ray cone-beam computed tomography (CBCT) is important for a precise radiation therapy for lung cancer. Due to the repeated use and 4D acquisition over a course of radiotherapy, the radiation dose becomes a concern. Meanwhile, the scatter contamination in CBCT deteriorates image quality for treatment tasks. In this work, we propose to use a moving blocker (MB) during the 4D CBCT acquisition ("4D MB") and to combine motion-compensated reconstruction to address these two issues simultaneously. In 4D MB CBCT, the moving blocker reduces the X-ray flux passing through the patie...
Source: Physics in Medicine and Biology - May 3, 2018 Category: Physics Authors: Zhao C, Zhong Y, Duan X, Zhang Y, Huang X, Wang J, Jin M Tags: Phys Med Biol Source Type: research

Robust real-time extraction of respiratory signals from PET list-mode data.
Abstract Respiratory motion, which typically cannot simply be suspended during PET image acquisition, affects lesions' detection and quantitative accuracy inside or in close vicinity to the lungs. Some motion compensation techniques address this issue via pre-sorting ("binning") of the acquired PET data into a set of temporal gates, where each gate is assumed to be minimally affected by respiratory motion. Tracking respiratory motion is typically realized using dedicated hardware (e.g. using respiratory belts and digital cameras). Extracting respiratory signalsdirectly from the acquired PET data simplifi...
Source: Physics in Medicine and Biology - May 1, 2018 Category: Physics Authors: Salomon A, Zhang B, Olivier P, Goedicke A Tags: Phys Med Biol Source Type: research

Markerless positional verification using template matching and triangulation of kV images acquired during irradiation for lung tumors treated in breath-hold.
Abstract Lung tumors treated in breath-hold are subject to inter- and intra-breath-hold variations, which makes tumor position monitoring during each breath-hold important. A markerless technique is desirable, but limited tumor visibility on kV images makes this challenging. We evaluated if template matching+triangulation of kV projection images acquired during breath-hold stereotactic treatments could determine 3D tumor position. Band-pass filtering and/or digital tomosynthesis (DTS) were used as image pre-filtering/enhancement techniques. On-board kV images continuously acquired during volumetric modulated arc i...
Source: Physics in Medicine and Biology - May 1, 2018 Category: Physics Authors: Hazelaar C, Dahele M, Mostafavi H, van der Weide L, Slotman BJ, Verbakel WFAR Tags: Phys Med Biol Source Type: research

A novel approach to EPID-based 3D volumetric dosimetry for IMRT and VMAT QA.
Abstract Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) are relatively complex treatment delivery techniques and require Quality Assurance (QA) procedures. Pre-treatment dosimetric verification represents a fundamental QA rocedure in daily clinical routine in radiation therapy. The purpose of this study is to develop an EPID-based approach to reconstruct a 3D dose distribution as imparted to a virtual cylindrical water phantom to be used for plan-specific pre-treatment dosimetric verification for IMRT and VMAT plans. For each depth, the planar 2D dose distributions acquire...
Source: Physics in Medicine and Biology - May 1, 2018 Category: Physics Authors: Alhazmi A, Gianoli C, Neppl S, Martins J, Veloza S, Podesta M, Verhaegen F, Reiner M, Belka C, Parodi K Tags: Phys Med Biol Source Type: research

Y-90 SPECT ML image reconstruction with a new model for tissue-dependent bremsstrahlung production using CT information: a proof-of-concept study.
Abstract While the yield of positrons used in Y-90 PET is independent of tissue media, Y-90 SPECT imaging is complicated by the tissue dependence of bremsstrahlung photon generation. The probability of bremsstrahlung production is proportional to the square of the atomic number of the medium. Hence, the same amount of activity in different tissue regions of the body will produce different numbers of bremsstrahlung photons. Existing reconstruction methods disregard this tissue-dependency, potentially impacting both qualitative and quantitative imaging of heterogeneous regions of the body such as bone with marrow ca...
Source: Physics in Medicine and Biology - May 1, 2018 Category: Physics Authors: Lim H, Fessler JA, Wilderman SJ, Brooks AF, Dewaraja YK Tags: Phys Med Biol Source Type: research

The biomechanics of simple steatosis and steatohepatitis.
Abstract Magnetic resonance and ultrasound elastography techniques are now important tools for staging high-grade fibrosis in patients with chronic liver disease. However, uncertainty remains about the effects of simple accumulation of fat (steatosis) and inflammation (steatohepatitis) on the parameters that can be measured using different elastographic techniques. To address this, we examine the rheological models that are capable of capturing the dominant viscoelastic behaviors associated with fat and inflammation in the liver, and quantify the resulting changes in shear wave speed and viscoelastic parameters. T...
Source: Physics in Medicine and Biology - April 27, 2018 Category: Physics Authors: Parker KJ, Ormachea J, Drage MG, Kim H, Hah Z Tags: Phys Med Biol Source Type: research

Gray: a ray tracing-based Monte Carlo simulator for PET.
Abstract Monte Carlo simulation software plays a critical role in PET system design. Performing complex, repeated Monte Carlo simulations can be computationally prohibitive, as even a single simulation can require a large amount of time and a computing cluster to complete. Here we introduce Gray, a Monte Carlo simulation software for PET systems. Gray exploits ray tracing methods used in the computer graphics community to greatly accelerate simulations of PET systems with complex geometries. We demonstrate the implementation of models for positron range, annihilation acolinearity, photoelectric absorption, Compton...
Source: Physics in Medicine and Biology - April 27, 2018 Category: Physics Authors: Freese DL, Olcott PD, Buss SR, Levin CS Tags: Phys Med Biol Source Type: research

Quantitative myocardial perfusion from static cardiac and dynamic arterial CT.
Abstract Quantitative myocardial blood flow (MBF) estimation by dynamic contrast enhanced cardiac computed tomography (CT) requires multi-frame acquisition of contrast transit through the blood pool and myocardium to inform the arterial input and tissue response functions. Both the input and the tissue response functions for the entire myocardium are sampled with each acquisition. However, the long breath holds and frequent sampling can result in significant motion artifacts and relatively high radiation dose. To address these limitations, we propose and evaluate a new static cardiac and dynamic arterial (SCDA) qu...
Source: Physics in Medicine and Biology - April 27, 2018 Category: Physics Authors: Bindschadler M, Branch KR, Alessio AM Tags: Phys Med Biol Source Type: research

Incorporating drug delivery into an imaging-driven, mechanics-coupled reaction diffusion model for predicting the response of breast cancer to neoadjuvant chemotherapy: theory and preliminary clinical results.
This study demonstrates the plausibility of using DCE-MRI data as a means to estimate drug delivery on a patient-specific basis in predictive models and represents a step toward the goal of achieving individualized prediction of tumor response to therapy. PMID: 29697054 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Jarrett AM, Hormuth Ii DA, Barnes SL, Feng X, Huang W, Yankeelov TE Tags: Phys Med Biol Source Type: research

Monte Carlo simulation of chemistry following radiolysis with TOPAS-nBio.
In conclusion, radiolysis and subsequent chemistry with Geant4-DNA has been successfully incorporated in TOPAS-nBio. Results are in reasonable agreement with published measured and simulated data. PMID: 29697057 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Ramos-Mendez JA, Perl J, Schuemann J, McNamara AL, Paganetti H, Faddegon BA Tags: Phys Med Biol Source Type: research

Toward minimizing annotation work: Diagnosis of mammographic masses via active learning.
Conclusions: By taking the particularities of mammographic images, the proposed AL method can indeed reduce the manual annotation work to a great extent without sacrificing performance of prediction system for mammographic diagnosis. . PMID: 29697059 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 26, 2018 Category: Physics Authors: Zhao Y, Zhang J, Xie H, Zhang S, Gu L Tags: Phys Med Biol Source Type: research

A combined positron emission tomography (PET)- electron paramagnetic resonance imaging (EPRI) system: initial evaluation of a prototype scanner.
Abstract The advent of hybrid scanners, combining complementary modalities, has revolutionized imaging; enhancing clinical practice and biomedical research. In this project, we investigated the melding of two complementary, functional imaging methods: positron emission tomography (PET) and electron paramagnetic resonance imaging (EPRI). The PET radiotracers can provide important information about cellular parameters, such as glucose metabolism. While EPR probes can provide assessment of tissue microenvironment, measuring parameters such as oxygenation and pH, for example. A combined PET/EPRI scanner has the promis...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: Tseytlin M, Stolin AV, Guggilapu P, Bobko AA, Khramtsov VV, Tseytlin O, Raylman RR Tags: Phys Med Biol Source Type: research

Comparison of fan beam, slit-slat and multi-pinhole collimators for molecular breast tomosynthesis.
Abstract Recently, we proposed and optimized dedicated multi-pinhole molecular breast tomosynthesis (MBT) that images a lightly compressed breast. As MBT may also be performed with other types of collimators, the aim of this paper is to optimize MBT with fan beam and slit-slat collimators and to compare its performance to that of multi-pinhole MBT to arrive at a truly optimized design. Using analytical expressions, we first optimized fan beam and slit-slat collimator parameters to reach maximum sensitivity at a series of given system resolutions. Additionally, we performed full system simulations of a breast phant...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: van Roosmalen J, Beekman FJ, Goorden MC Tags: Phys Med Biol Source Type: research

Automated human skull landmarking with 2D gabor wavelets.
We present a novel method for automatically locating anatomical landmarks on the surface of cone beam CT-based image models of human skulls using 2D Gabor wavelets and ensemble learning. The algorithm is validated via human inter- and intra-rater comparisons on a set of 39 scans and a skull superimposition experiment with an established surgery planning software (Maxilim). Automatic landmarking results in an accuracy of 1-2 mm for a subset of landmarks around the nose area as compared to a gold standard derived from human raters. These landmarks are located in eye sockets and lower jaw, and is competitive with or surpasses...
Source: Physics in Medicine and Biology - April 20, 2018 Category: Physics Authors: de Jong MA, Gül A, de Gijt JP, Koudstaal MJ, Kayser M, Wolvius EB, Böhringer S Tags: Phys Med Biol Source Type: research

Motion induced interplay effects for VMAT radiotherapy.
In conclusion, a method to simulate motion induced interplay effects was developed and verified with measurements, which allowed for a large number of treatment scenarios to be investigated. The simulations showed large interplay effects for individual fractions and that the extent of interplay effects varied with the breathing pattern, FFF/FF, dose level, CTV size, collimator angle, and the complexity of the treatment plan. PMID: 29671410 [PubMed - in process] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 19, 2018 Category: Physics Authors: Edvardsson A, Nordström F, Ceberg C, Ceberg S Tags: Phys Med Biol Source Type: research

A random phased-array for MR-guided transcranial ultrasound neuromodulation in non-human primates.
Abstract Transcranial focused ultrasound (FUS) is a non-invasive technique for therapy and study of brain neural activation. Here we report on the design and characterization of a new MR-guided FUS transducer for neuromodulation in non-human primates at 650 kHz. The array is randomized with 128 elements 6.6 mm in diameter, radius of curvature 7.2 cm, opening diameter 10.3 cm (focal ratio 0.7), and 46% coverage. Simulations were used to optimize transducer geometry with respect to focus size, grating lobes, and directivity. Focus size and grating lobes during electronic steering were quantified using hydrophone mea...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Chaplin V, Phipps MA, Caskey CF Tags: Phys Med Biol Source Type: research

Applying a new computer-aided detection scheme generated imaging marker to predict short-term breast cancer risk.
This study aims to investigate the feasibility of identifying a new quantitative imaging marker based on false-positives generated by computer-aided detection (CAD) scheme to help predict short-term breast cancer risk. An image dataset including four view mammograms acquired from 1,044 women was retrospectively assembled. All mammograms were originally interpreted as negative by radiologists. In the next subsequent mammography screening, 402 women were diagnosed with breast cancer and 642 remained negative. An existing CAD scheme was applied "as is" to process each image. From CAD-generated results, 4 detection f...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Mirniaharikandehei S, Hollingsworth AB, Patel B, Heidari M, Liu H, Zheng B Tags: Phys Med Biol Source Type: research

A CBCT study of the gravity-induced movement in rotating rabbits.
Abstract Fixed-beam radiotherapy systems with subjects rotating about a longitudinal (horizontal) axis are subject to gravity-induced motion. Limited reports on the degree of this motion, and any deformation, has been reported previously. The purpose of this study is to quantify the degree of anatomical motion caused by rotating a subject around a longitudinal axis, using cone-beam CT (CBCT). In the current study, a purpose-made longitudinal rotating was aligned to a Varian TrueBeam kV imaging system. CBCT images of three live rabbits were acquired at fixed rotational offsets of the cradle. Rigid and d...
Source: Physics in Medicine and Biology - April 18, 2018 Category: Physics Authors: Barber J, Shieh CC, Counter W, Sykes JR, Bennett P, Ahern V, Corde S, Heng SM, White P, Jackson M, Liu P, Keall PJ, Feain I Tags: Phys Med Biol Source Type: research

Time-of-flight PET time calibration using data consistency.
Abstract This paper presents new data driven methods for the time of flight (TOF) calibration of positron emission tomography (PET) scanners. These methods are derived from the consistency condition for TOF PET, they can be applied to data measured with an arbitrary tracer distribution and are numerically efficient because they do not require a preliminary image reconstruction from the non-TOF data. Two-dimensional simulations are presented for one of the methods, which only involves the two first moments of the data with respect to the TOF variable. The numerical results show that this method estimate...
Source: Physics in Medicine and Biology - April 17, 2018 Category: Physics Authors: Defrise M, Rezaei A, Nuyts J Tags: Phys Med Biol Source Type: research

GPU-based Green's function simulations of shear waves generated by an applied acoustic radiation force in elastic and viscoelastic models.
Abstract Shear wave calculations induced by an acoustic radiation force are very time-consuming on desktop computers, and high-performance graphics processing units (GPUs) achieve dramatic reductions in the computation time for these simulations. The acoustic radiation force is calculated using the fast near field method (FNM) and the angular spectrum approach (ASA), and then the shear waves are calculated in parallel with Green's functions on a GPU. This combination enables rapid evaluation of shear waves for push beams with different spatial samplings and for apertures with different f/#. Relative to shear wave ...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Yang Y, Urban MW, McGough RJ Tags: Phys Med Biol Source Type: research

Novel inter-crystal scattering event identification method for PET detectors.
In conclusion, our proposed method showed good ICS identification in both 1-to-1 coupling and light sharing detectors. We experimentally validated that ICS recovery based on the proposed identification method led to improved resolution. . PMID: 29658493 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Lee MS, Kang SK, Lee JS Tags: Phys Med Biol Source Type: research

Multi-resolution simulation of focused ultrasound propagation through ovine skull from a single-element transducer.
Abstract Transcranial focused ultrasound (tFUS) is emerging as a non-invasive brain stimulation modality. Complicated interactions between acoustic pressure waves and osseous tissue introduce many challenges in the accurate targeting of an acoustic focus through the cranium. Image-guidance accompanied by a numerical simulation is desired to predict the intracranial acoustic propagation through the skull; however, such simulations typically demand sophisticated computation, which warrants an expedited processing method to provide on-site feedback for the user in guiding the acoustic focus to a particular brain regi...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Yoon K, Lee W, Croce P, Cammalleri A, Yoo SS Tags: Phys Med Biol Source Type: research

Cross-correlation analysis of pulse wave propagation in arteries: < i > in vitro < /i > validation and < i > in vivo < /i > feasibility.
Cross-correlation analysis of pulse wave propagation in arteries: in vitro validation and in vivo feasibility. Phys Med Biol. 2018 Apr 16;: Authors: Nauleau P, Apostolakis IZ, McGarry M, Konofagou EE Abstract The stiffness of the arteries is known to be an indicator of the progression of various cardiovascular diseases. Clinically, the pulse wave velocity (PWV) is used as a surrogate for the arterial stiffness. Pulse Wave Imaging (PWI) is a non-invasive, ultrasound-based imaging technique capable of mapping the motion of the vessel walls allowing local assessment of the arterial properties. Convention...
Source: Physics in Medicine and Biology - April 16, 2018 Category: Physics Authors: Nauleau P, Apostolakis IZ, McGarry M, Konofagou EE Tags: Phys Med Biol Source Type: research

Multi-layer imager design for mega-voltage spectral imaging.
Abstract The architecture of multi-layer imagers (MLIs) can be exploited to provide megavoltage spectral imaging (MVSPI) for specific imaging tasks. In the current work, we investigated bone suppression and gold fiducial contrast enhancement as two clinical tasks which could be improved with spectral imaging. A method based on analytical calculations that enables rapid investigation of MLI component materials and thicknesses was developed and validated against Monte Carlo computations. The figure of merit for task-specific imaging performance was the contrast-to-noise ratio (CNR) of the gold fiducial when the CNR ...
Source: Physics in Medicine and Biology - April 13, 2018 Category: Physics Authors: Myronakis ME, Hu YH, Fueglistaller R, Wang A, Baturin P, Huber P, Morf D, Star-Lack JM, Berbeco RI Tags: Phys Med Biol Source Type: research

Design of a QA method to characterize submillimeter-sized PBS beam properties using a two-dimensional ionization chamber array.
Abstract Pencil beam scanning (PBS) periodic quality assurance (QA) programs ensure the beam delivered to patients is within technical specifications. Two critical specifications for PBS delivery are the beam width and position. The aim of this study is to investigate whether a 2-dimensional ionization chamber array, such as the MatriXX detector (IBA Dosimetry, Schwarzenbruck, Germany), can be used to characterize submillimeter-sized PBS beam properties. The motivation is to use standard equipment, which may have pixel spacing coarser than the pencil beam size, and simplify QA workflow. The MatriXX pixels ar...
Source: Physics in Medicine and Biology - April 12, 2018 Category: Physics Authors: Lin Y, Bentefour EH, Flanz JB, Kooy HM, Clasie BM Tags: Phys Med Biol Source Type: research

Markerless motion estimation for motion-compensated clinical brain imaging.
Abstract Motion-compensated brain imaging can dramatically reduce the artifacts and quantitative degradation associated with voluntary and involuntary subject head motion during positron emission tomography (PET), single photon emission computed tomography (SPECT) and computed tomography (CT). However, motion-compensated imaging protocols are not in widespread clinical use for these modalities. A key reason for this seems to be the lack of a practical motion tracking technology allowing for smooth and reliable integration of motion-compensated imaging protocols in the clinical setting. We address this problem by i...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Kyme AZ, Se S, Meikle SR, Fulton RR Tags: Phys Med Biol Source Type: research

Dosimetric characteristics of the University of Washington clinical neutron therapy system.
Abstract The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer (LET) fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360&lt;sup&gt;○&lt;/sup&gt; of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3,178 patients have received conformal neutron therapy treatments usin...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Moffitt GB, Stewart RD, Sandison GA, Goorley JT, Argento DC, Jevremovic T, Emery R, Wootton LS, Parvathaneni U, Laramore GE Tags: Phys Med Biol Source Type: research

Realistic modeling of deep brain stimulation implants for electromagnetic MRI safety studies.
Abstract We propose a framework for electromagnetic (EM) simulation of deep brain stimulation (DBS) patients in radiofrequency (RF) coils. We generated a model of a DBS patient using post-operative head and neck computed tomography (CT) images stitched together into a "virtual CT" image covering the entire length of the implant. The body was modeled as homogeneous. The implant path extracted from the CT data contained self-intersections, which we corrected automatically using an optimization procedure. Using the CT-derived DBS path, we built a model of the implant including electrodes, helicoidal interna...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Guerin B, Serano P, Iacono MI, Herrington TM, Widge AS, Dougherty DD, Bonmassar G, Angelone LM, Wald LL Tags: Phys Med Biol Source Type: research

Lesion detectability in 2D-mammography and digital breast tomosynthesis using different targets and observers.
Abstract This work investigates the detection performance of specialist and non-specialist observers for different targets in 2D-mammography and digital breast tomosynthesis (DBT) using the OPTIMAM Virtual Clinical Trials (VCT) Toolbox and a 4-alternative forced choice (4AFC) assessment paradigm. Using 2D-mammography and DBT images of virtual breast phantoms, we compare the detection limits of simple uniform spherical targets and irregular solid masses. Target diameters of 4mm and 6mm have been chosen to represent target sizes close to the minimum detectable size found in breast screening, across a rang...
Source: Physics in Medicine and Biology - April 11, 2018 Category: Physics Authors: Elangovan P, Mackenzie A, Dance DR, Young KC, Wells K Tags: Phys Med Biol Source Type: research

Stable gelatin-based phantom materials with tunable x-ray attenuation properties and 3D printability for x-ray imaging.
We report a novel method for developing gelatin-based phantom materials for transmission x-ray imaging with high stability at room temperature and tunable x-ray attenuation properties. This is achieved by efficiently cross-linking gelatin in a glycerin solution with only 10% water by volume and systematically decreasing their x-ray attenuation coefficients by doping with microbubbles that are originally designed to be used as lightweight additives for paints and crack fillers. For demonstration, we mimic breast glandular and adipose tissues by using such gelatin materials and also study the feasibility of 3D printing ...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Dahal E, Badal A, Zidan A, Alayoubi A, Hagio T, Glick SJ, Badano A, Ghammraoui B Tags: Phys Med Biol Source Type: research

Multi-threading performance of Geant4, MCNP6, and PHITS Monte Carlo codes for tetrahedral-mesh geometry.
Abstract In the present study, the multi-threading performances of the Geant4, MCNP6, and PHITS codes were evaluated as a function of the number of the threads (N) and the complexity of the tetrahedral-mesh phantom. For this, three tetrahedral-mesh phantoms with different complexity (simple, moderately complex, and highly complex) were prepared and implemented in three different Monte Carlo codes, carrying out photon and neutron transport simulations. Subsequently, for each case, the initialization time, calculation time, and memory usage were measured as a function of the number of threads used in the simulation....
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Han MC, Yeom YS, Lee HS, Shin B, Kim CH, Furuta T Tags: Phys Med Biol Source Type: research

Inverse optimization of objective function weights for treatment planning using clinical dose-volume histograms.
Abstract We developed and evaluated a novel inverse optimization (IO) model to estimate objective function weights from clinical dose-volume histograms (DVHs). These weights were used to solve a treatment planning problem to generate "inverse plans" that had similar DVHs to the original clinical DVHs. Our methodology was applied to 217 clinical head and neck cancer treatment plans that were previously delivered at Princess Margaret Cancer Centre in Canada. Inverse plan DVHs were compared to the clinical DVHs using objective function values, dose-volume differences, and frequency of clinical planning crit...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Babier A, Boutilier JJ, Sharpe MB, McNiven AL, Chan TCY Tags: Phys Med Biol Source Type: research

MR-ARFI-based method for quantitative measurement of tissue elasticity: application to monitoring of HIFU therapy.
Abstract Monitoring thermal therapies thanks to medical imaging is essential in order to ensure that they are safe, efficient and reliable. In this paper, we propose a new approach, halfway between MR Acoustic Radiation Force Imaging (MR-ARFI) and MR Elastography (MRE), allowing for quantitative measurement of tissue's elastic modulus in a highly localized manner. It relies on the simulation of the MR-ARFI profile, which depends on tissue biomechanical properties, and on the identification of tissue elasticity through the fitting of the experimental displacement images measured using rapid MR-ARFI. Such method was...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Vappou J, Bour P, Marquet F, Ozenne V, Quesson BAJ Tags: Phys Med Biol Source Type: research

Superpixel-based and boundary-sensitive convolutional neural network for automated liver segmentation.
Conclusion: SBBS-CNN provides an accurate and effective tool for automated liver segmentation. It is also envisioned that the proposed framework is directly applicable in other medical image segmentation scenarios. . PMID: 29633960 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Qin W, Wu J, Han F, Yuan Y, Zhao W, Ibragimov B, Gu J, Xing L Tags: Phys Med Biol Source Type: research

Computation of reliable textural indices from multimodal brain MRI: suggestions based on a study of patients with diffuse intrinsic pontine glioma.
Abstract Few methodological studies regarding widely used textural indices robustness in MRI have been reported. In this context, this study aims at proposing some rules to compute reliable textural indices from multimodal 3D brain MRI. Diagnosis and post-biopsy MR scans including T1, post-contrast T1, T2 and FLAIR images from thirty children with diffuse intrinsic pontine glioma (DIPG) were considered. The Hybrid White Stripe method was adapted to standardize MR intensities. Sixty textural indices were then computed for each modality in different regions of interest, including tumor and white matter (WM). Three t...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Goya-Outi J, Orlhac F, Calmon R, Alentorn A, Nioche C, Philippe C, Puget S, Boddaert N, Buvat I, Grill J, Frouin V, Frouin F Tags: Phys Med Biol Source Type: research

Characterization of the exradin W1 plastic scintillation detector for small field applications in proton therapy.
This study examines the dosimetric performance of the W1 in a 74 MeV proton therapy beam with particular focus on detector response characteristics relevant to relative dose measurement in small fields suitable for ocular therapy. Quenching of the scintillation signal is characterized and demonstrated not to impede relative dose measurements at a fixed depth. The background cable-only (Čerenkov and radio-fluorescence) signal is 4 orders of magnitude less than the scintillation signal, greatly simplifying relative dose measurements. Comparison with other detectors and Monte Carlo simulations indicate that the W1 is useful ...
Source: Physics in Medicine and Biology - April 10, 2018 Category: Physics Authors: Hoehr C, Lindsay C, Beaudry J, Penner C, Strgar V, Lee R, Duzenli C Tags: Phys Med Biol Source Type: research

Tetrazolium salts-Pluronic F-127 gels for 3D radiotherapy dosimetry.
Abstract This work is a follow-up study for a recently-proposed 3D radiochromic gel dosimeter that contains a tetrazolium salt and a physical gel matrix made of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127). Several tetrazolium salts were examined in this work, including tetrazolium violet (TV), blue tetrazolium chloride (BT), nitro blue tetrazolium chloride (NBT), tetranitro blue tetrazolium chloride (tNBT) and thiazolyl blue tetrazolium bromide (TBTB). The salt-containing gel dosimeters were compared with the first Pluronic gel composition that contained 2,3,5-triph...
Source: Physics in Medicine and Biology - April 5, 2018 Category: Physics Authors: Kwiatos K, Maras P, Kadlubowski S, Stempień Z, Dudek M, Kozicki M Tags: Phys Med Biol Source Type: research

Introduction of a hybrid treatment delivery system used for quality assurance in multi-catheter interstitial brachytherapy.
Abstract Multi-catheter interstitial brachytherapy (iBT) is a treatment option for breast cancer patients after breast conserving surgery. Typically, only a few additional quality interventions after the first irradiation have been introduced to ensure the planned treatment delivery. Therefore, the purpose of this study is to show the possibilities of an electromagnetic tracking (EMT) system integrated into the afterloader for quality assurance (QA) in high-dose rate (HDR) iBT of patients with breast cancer. The hybrid afterloader system equipped with an electromagnetic sensor was used for all phantom and pa...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Kallis K, Kreppner S, Lotter M, Strnad V, Fietkau R, Bert C Tags: Phys Med Biol Source Type: research

Evolutionary pruning of transfer learned deep convolutional neural network for breast cancer diagnosis in digital breast tomosynthesis.
The objective is to prune the number of tunable parameters while preserving the classification accuracy. In the first stage transfer learning, 19,632 augmented regions-of-interest (ROIs) from 2,454 mass lesions on mammograms were used to train a pre-trained DCNN on ImageNet. In the second stage transfer learning, the DCNN was used as a feature extractor followed by feature selection and random forest classification. The pathway evolution was performed using genetic algorithm in an iterative approach with tournament selection driven by count-preserving crossover and mutation. The second stage was trained with 9,120 DBT ROIs...
Source: Physics in Medicine and Biology - April 4, 2018 Category: Physics Authors: Samala RK, Chan HP, Hadjiiski LM, Helvie MA, Richter C, Cha K Tags: Phys Med Biol Source Type: research